| A |
| abraded culet |
A chipped or scratched culet. Can be caused by contact with
another diamond. |
| abrasion |
A bruise
or scratch on the surface of a stone. |
| AGS |
American Gem Society. Professional organization
formed in 1934 by several independent jewelers and the founder of the
Gemological Institute of America (GIA). The AGS is dedicated to
setting and maintaining ethical standards and practices within the
industry. |
| Antwerp |
Perhaps the most noteworthy and versatile diamond-cutting center in
the world. All sizes and shapes of rough diamonds are cut in
Antwerp. |
| appraisal |
A
monetary evaluation, usually performed for insurance purposes by a
gemologist. Appraisals should describe the piece in detail,
including color, clarity, proportions, stone sizes, flaws and other
distinguishing characteristics. |
| B |
| baguette |
A
rectangular cut stone with squared corners. |
| bearding |
Small
feather-like cracks along the girdle of a diamond. |
| bezel |
Outer
ring of a watch case, usually designed to hold the crystal, that may also
be used for advanced functions like diving timers. |
| bezel
setting |
Holds a
gemstone in place on all sides at the girdle, creating a smooth, metal
halo flush with the stone's crown. Bezel settings often give the
impression of a larger stone. |
| blemish |
A flaw,
spot or scratch on the surface of a gemstone. |
| brilliance |
The
intensity and amount of light reflecting from inside a diamond or
gemstone. |
| brilliant cut |
The most
common style of cutting for diamonds and colored stones. Brilliant
cuts may be round or fancy and must have 57 or 58 facet cuts. |
| C |
| cabochon |
A
gemstone cut that creates a dome shape with no facets. |
| caliper |
Instrument for determining the thickness or diameter of a
gemstone. |
| carat |
One of
the "Four Cs". Metric unit of weight for diamonds and
gemstones. One carat equals 200 milligrams or 0.2
grams. |
| clarity |
One of
the "Four Cs". Measures the degree to which a gemstone is free from
flaws. A clarity scale is used to grade flaws in gemstones.
The scale ranges from FL (Flawless) where there are no visible internal or
external flaws to I3, where many imperfections are visible to the naked
eye. |
| cleavage |
Tendency
of a crystalline material to break in certain directions, often along a
grain or crystal face. |
| cloud |
Group of
tiny white inclusions in a diamond. |
| color |
One of
the "Four Cs". In diamonds, the color scale ranges from D
(colorless) to Z (yellow). In colored gemstones, the grading scale
differs widely depending on the type of stone. |
| comfort fit |
Ring
design in which the edges of the shank are rounded for maximum
comfort. |
| crown |
The
facets or portions of a gemstone located above the girdle. |
| culet |
A small
polished facet located at the sharp point or base of a faceted diamond or
gemstone. |
| cultured pearl |
Pearls
created by the artificial introduction of a mother-of-pearl irritant into
an oyster or other mollusk. Cultured pearls generally have thinner
nacre and lack the luster of a natural pearl. |
| cut |
One of
the "Four Cs". Perhaps the most important factor in determining the
value of a diamond or gemstone. The cut refers to the geometric
proportion that dictates the reflection and refraction of light within a
stone. |
| D |
| depth |
The
distance from a gemstone's table to its culet (top to
bottom). |
| depth
percentage |
The
measurement of a gemstone's depth (top to bottom) in relation to its
diameter. Depth percentage is primarily responsible for refraction,
which produces the fire or sparkle in a gemstone. |
| Diamond Gauge |
A
mechanical device used to determine the precise measurements of a
gemstone. |
| DiamondLite |
Instrument for color grading diamonds using visual comparisons to
master diamonds. Trademark, Gemological Institute of
America. |
| dispersion |
The
separation of white light into the full color spectrum. Often
described as the "fire" or sparkle when discussing diamonds. |
| E |
| emerald cut |
Step cut
gemstone (most often rectangular) whose corners have been cut
off. |
| extinction |
Dark or
black spots in colored stone. |
| eye-clean |
Gemstone
in which the flaws cannot be seen without a 10x loupe. |
| F |
| facet |
Flat,
polished surface or plane on a gemstone. |
| faceted girdle |
Girdle
that has been cut with facets. |
| fancy
shapes |
A
gemstone shape other than round. |
| feather |
Internal
flaw (inclusion) that has a feathery appearance. |
| findings |
Small,
pre-fabricated parts of jewelry such as clasps, settings,
etc. |
| fire |
The sparkles of flashes of spectral colors emitted from diamonds
and other gemstones. |
| flaw |
General
term used to refer to internal or external characteristics of a gemstone
(i.e., inclusion, fracture, etc) |
| flawless |
Term used
to describe a gemstone that lacks discernable internal or external
blemishes when viewed by a gemologist using no less than 10x
magnification. |
| fluorescence |
Luminescence that appears when certain diamonds are exposed to
ultraviolet light. |
| fracture |
Cracks,
feathers or chips in a gemstone. |
| full
cut |
Gemstone
with 58 facets. |
| G |
| gemologist |
Gemstone
specialist trained in gem identification, grading and
appraising. |
| gemology |
Science
and study of gemstones. |
| GIA |
Gemological Institute of America. Non-profit organization
specializing in grading diamonds and gemstones. Widely held as the
premier laboratory for gemological grading. |
| girdle |
The
narrow rim around a gemstone separating the crown from the
pavilion. |
| gold
filled |
Metal
covered by a thin layer of gold that is at least 10k and 1/20th of the
total weight of the piece |
| gold
plated |
Virtually
the same as gold filled, except gold plated items may have a layer of gold
that is less than 1/20th of the total weight of the piece |
| grading |
Valuing a
diamond using master stones. |
| H |
| head |
Portion
of a jewelry item that holds the stone. |
| I |
| IJO |
|
| imperfection |
General
term used to refer to internal or external characteristics of a gemstone
(i.e., inclusion, fracture, etc) |
| inclusion |
Visible
internal flaws in a gemstone, including fractures, crystalling
abnormalities, and foreign objects. |
| irradiation |
Treatment
performed on gemstones and even pearls to enhance color. |
| K |
| karat |
Standard
measure of gold purity. One karat is 1/24th pure. |
| L |
| laser
drilling |
Technique
used to enhance a stone's clarity by allowing for the introduction of
bleaching agents or other enhancing agents. |
| leakage |
Light
leaving, or escaping, through the facets of fashioned
gemstone. |
| Leveridge gauge |
A
millimeter gauge used to measure both mounted and unmounted
stones. |
| loupe |
Small
magnifying glass, often held in the eye socket, used for analyzing
gemstones. |
| luster |
The
appearance of a material's surface, as determined by the quantity and
quality of light reflected. |
| M |
| marquise |
Oval
shaped gemstone with ends sharpened to points. |
| master
stones |
A set of
diamonds used to grade the color of other diamonds. |
| milgrain |
Tiny
beads of metal used to decorate bands of metal |
| Moh's
Scale |
Scale
used to measure gemstone hardness. Scale ranges from 1 to
10. |
| mounting |
Method of
holding gemstones in place (i.e., prongs, bezels, etc) |
| N |
| nacre |
Crystalline substance that forms a pearl when secreted by a mollusk
in response to an irritant. |
| O |
| off
color |
A stone
presenting any semblance of undesirable color. |
| oiling |
Temporary
treatment used to enhance the color of a gemstone. |
| opera |
A strand
of pearls 32 inches in length. |
| P |
| pave
(pah-vay') setting |
Style of
setting small stones as close together as possible. Stones are set
into drilled holes and metal beads are pushed over to hold the
stone. |
| pavilion |
The
portion of a gemstone located below the girdle. |
| percussion mark |
Indentation or bruise on the surface of a gemstone caused by
contact from a pointed object. |
| pit |
Indentation on the surface of a diamond or gemstone. |
| platinum |
Precious
metal that is far harder than gold. Platinum does not tarnish and is
hypo-allergenic. |
| plot |
Diagram
of a gemstone's clarity characteristics. Generally performed during
an appraisal using magnification. |
| point |
One-one
hundredth (0.01) of a carat. |
| princess |
A strand
of pearls 18 inches in length. |
| princess cut |
Square
cut, brilliant gemstone. |
| prong |
Metal
"finger" bent around the girdle of a gemstone to hold it securely in
place. |
| proportion |
Mathematical representation of a gemstone's overall
symmetry. |
| R |
| recutting |
Refinishing a polished stone in order to improve the stone's
clarity, proportion or other imperfection. |
| reflection |
Light
rebounding off the polished surfaces of a gemstone. |
| refraction |
Bending
of light waves. When white light is refracted, a full spectrum of
color appears, as in a prism. |
| rope |
A strand
of pearls 40 inches in length. |
| rough |
An uncut
or unpolished diamond or gemstone. |
| S |
| setting |
Method of
holding gemstones in place (i.e., prongs, bezels, etc) |
| shank |
Part of
the ring that encircles the finger. |
| single
cut |
A simple
form of cutting that has a table, approximately 16 facets and rarely a
culet. |
| solitaire |
Ring
containing a single diamond or gemstone. |
| symmetry |
Uniformity of a gemstone's cut, including the shape and placement
of facets. |
| synthetic stone |
"Man-made" gemstone grown in a lab. |
| T |
| table |
Largest
facet on a gemstone. The table sits atop the crown and allows light
to enter and exit, creating the stone's brilliance. |
| table
percentage |
Diameter
of a gemstone divided by the size of the table. |
| Tolkowsky, Marcel |
Mathematician that defined the proportions necessary for maximum
brilliance from a round diamond brilliant cut |
| U |
| ultrasonic |
Cleaning
device for jewelry that removes dirt through the use of ultrasonic
waves. Note: Certain gemstones may be damaged by an ultrasonic
cleaner. |